Meta

Category: Cool Research

Today I received my November 2012 issue of Arboriculture and Urban Forestry. This is one of the few peer-reviewed journals that generally has information of immediate value to gardeners and landscape professionals as well as academics. This issue contains an article entitled “Evaluation of biostimulants to control Guignardia leaf blotch (Guignardia aesculi) of horsechestnut and black spot (Diplocarpon rosae) of roses.” (And before you ask, no, I can’t attach the article or link to it. You’ll need to read it in the journal itself or wait for a year when the organization makes it available to everyone.)

Anyway, this study looked at eight different self-identified biostimulants, including Superthirve (which every gardener must have heard of by now). In addition to Superthrive, the other products tested were Maxicrop Original, Resistim, Bioplex, Fulcrum CRV, Redicrop, Crop Set, and Systhane. Purported active ingredients within this group include seaweed extract, molasses, vitamin B, and Lactobacillus fermentation product.

And the $64,000 question – did they work? Here’s the authors’ summary: “Irrespective of pathogen or concentration applied, none of the biostimulants used in this investigation provided a significant degree of Guignardia leaf blotch or black spot control compared to water-treated controls.” In other words, you can expect the same results by spraying your black spot-infested roses with water compared to any of these biostimulant products.

The authors end their article with a caveat sure to warm the cockles of every Garden Professor’s heart: “Results of this study indicate that where independent scientific data are not available to support the pathogen control claims of the manufacturer, then using an unevaluated biostimulant for this purpose is not recommended.”

(I’m glad this article is finally out. I was one of the peer reviewers for it, and I’ve been wanting to share the results on the blog ever since I read it.)

Every once in awhile I get to work with really, really cool people who do really, really cool work. This is one of those times. About a year ago I received a message from Dr. Stephanie Valberg, a Professor over at the University of Minnesota’s Equine Center. It seems that she was interested in looking at a deadly disease called Seasonal Pasture Myopathy which she thought might have something to do with horses ingesting maple leaves. Specifically, at the time she contacted me, she thought that this disease might be associated with horses ingesting tar spot, a common disease that maples get. Seasonal Pasture Myopathy is a particularly nasty disease because it is fatal in over 90% of cases, and the death is far from painless.

After doing site visits to many farms where this disease was found, she discovered something very important: Every farm had box elders in a location where horses could feed on the seed when they got hungry. And for most of the farms, horses were also dealing with scant pickings in terms of food. They usually had sparse pastures and not much supplemental hay. So, in these conditions, the horses might find box elder seed attractive, or at least palatable.

After a literature search, Dr. Valberg discovered an old article showing that box elder seeds could very well contain a toxin, hypoglycin A, which might cause this disease if they were eaten. After testing the seeds for the presence of this toxin (Done by a friend of mine, Adrian Hegeman, located here in the University of Minnesota’s Department of Horticultural Science) it was established that, Yep, box elder seeds have this toxin, and if your horse eats them, it might be in trouble. You can find out more here.

Right now more work is going on to see if this toxin is more or less present in box elder trees that are under stress, if it is present in other parts of the tree besides the seeds, and at what time of year the toxin might be most present in the seeds. It also looks as though some other maples may have this toxin in their seeds, most notably sycamore maple.

All in all, having the opportunity to watch this work unfold has been one of the highlights of my career. It was like watching an episode of House unfold in real life. And the great part is that this work has the potential to save the lives of dozens, if not hundreds or thousands, of animals. So if you have horses, and box elder or sycamore maples in your pasture, be careful!

I’m doing a webinar for WSU Extension folks next week with the decidedly unsexy title of "How to run literature searches when writing extension publications and how to develop client material using the information from the lit search." In reality, it’s how to research gardening topics, identify the myths (those practices and products with no basis in science), and then write up the valid scientific parts for use by gardeners. I’d hoped to get some ideas from this group on specific topics to demonstrate the process, but have gotten nothing. And I’m doing this a week from tomorrow.

So…how about you all? What practices or products that we’ve covered on this blog (or haven’t) that you’d like to see put through my sorting process? I don’t think people outside the WSU system can watch the webinar, but I’d be willing to post something on the blog about it later.

Feel free to comment below – the earlier the better, as I have to have this done by the end of the week so I can develop the presentation. And thanks in advance for your ideas!

I’ve been collecting data on above-ground growth during this year, but have had an unexpected twist to my research, as shown here:

That’s a pine tree.

Yes, we have moles…BIG moles apparently…in Puyallup. There’s not much I can do besides move the soil away, but obviously the pine trees are not going to be happy with this additional treatment. The maples are tall enough where it’s not going to be much of an issue.

Note to self: next time install guard Dachshunds next to pine trees. (Thanks to the Fremont Tribune for this great photo!)

Some environmental extremists discount agricultural research done by universities, because they receive funding from Big Ag and therefore their researchers can’t be trusted. So this news report of a recent study by one of my Washington State University colleagues is doubly important: it dispells this baseless assertion and it provides some significant – and troubling – information about pesticide use and GMO crops.

Briefly, the article links an increased use of herbicides as a result of increased use of GMOs such as Roundup-ready crops. Weeds build up resistance to herbicides over time, meaning that Roundup becomes less useful as a weed killer and farmers have to turn to more toxic substitutes like 2,4-D to control weeds.

Dr. Benbrooks’s results, published in a peer-reviewed journal, are contested by the chemical industry, and other scientists question the seriousness of the problem. But next time you hear someone malign university scientists as being in Monsanto’s back pocket, please refer them to this post.

Back in June of 2010, I wrote about an online column that recommended applying cornmeal as an antifungal soil amendment. (Important note: we are not talking about corn gluten meal. Just cornmeal.) The upshot of the post was while some gardening personalities extol the use of cornmeal to kill soil pathogens like Rhizoctonia and Sclerotinia, no published science supports the practice. The post was effective in encouraging the author of the referenced online column to update her information, but the controversy didn’t die. In fact, new comments have been added to the original post on a fairly consistent basis, mostly in the form of personal anecdotes or angry rebuttals. Some commenters, however, have tried to carry on rational discussions, so today we’re going to look at cornmeal from a slightly different angle: what effect does it have on microbes in general?

To start, let’s look at the Stephensville, Texas research that’s most often highlighted by cornmeal proponents. There’s no peer-reviewed work published on this specific research, but in an online copy of the Texas Peanut Production Guide I found a paragraph referring to “Biological Control of Soil-Borne Fungi.” Here it is in its entirety:

“Certain fungal species in the genus Trichoderma feed on mycelium and sclerotia of Sclerotinia minor, Sclerotium rolfsii and Rhizoctonia spp. All peanut fields in Texas tested to date have natural populations of Trichoderma. For several years, tests have been conducted in Texas using corn meal to stimulate Trichoderma development as a way to control the major soil-borne disease fungi. When yellow corn meal is applied to fields in the presence of moist surface soil, Trichoderma builds up very rapidly over 5 to 10 days. The resulting high Trichoderma population can destroy vast amounts of Sclerotinia, Sclerotium and Rhizoctonia. This enhanced, natural biological control process is almost identical to the processes that occur when crop rotation is practiced. The level of control with corn meal is influenced by organic matter source, soil moisture, temperature and pesticides used. Seasonal applications of certain fungicides may inhibit Trichoderma. Testing will continue to determine the rates and application methods that will give consistent, economical control.”

And that’s all there is on the topic. Most scientists would conclude that further testing was inconsistent and the researchers abandoned their efforts without publishing anything further. But this summary is at least a starting point, though it contains no data, references, or even authors.

First, there’s no argument that Trichoderma is a powerful antagonist of some nasty pathogenic fungi. Likewise, cornmeal most certainly can encourage the growth of Trichoderma, both in the lab and the field. But cornmeal also encourages the growth of many other fungi – in fact cornmeal agar is commonly used for culturing fungi in the lab. So what about those three pathogenic fungi mentioned in the Texas peanut guide? Do they like cornmeal?

Indeed they do! Published research (about 20 or so articles) shows that cornmeal (not cornmeal agar) has been used to enhance growth of Rhizoctonia fragariae, R. repens and R. solani, Sclerotinia sclerotiorum and S. homoeocarpa, and Sclerotium rolfsii. In some cases the pathogens became more virulent in the presence of cornmeal.

Cornmeal is nothing more than a carbohydrate-rich resource that can be used by many microbes. If you happen to have a lot of beneficial fungi in your soil, cornmeal will feed them. If you happen to have pathogenic species in your soil, cornmeal will feed them too. So it depends on what fungi are already living in your lawn, vegetable garden, or rose bed on whether cornmeal will help, or just make disease problems worse.

The best thing to do – as the paragraph from the peanut guide suggests – is to mix things up a little in your landscape. Use mixtures of lawn grasses rather than growing a monocultural turf. Rotate plant placement in your vegetable garden every year. Add a microbe-rich organic mulch to your rose beds. Natural methods will keep pathogens in check much more effectively than a hyped-up home remedy that’s anything but antifungal.

UPDATE: Since this is a myth that refuses to die, I’ve published a peer-reviewed fact sheet on the topic. Feel free to pass on to others.

Not to horn in on Bert’s posting day….but I was just sent this link to Iowa State’s compendium of research reports on nontraditional materials. Though this database is targeted towards crop production methods, there may be nuggets of information relevant to home gardens as well. And it includes a product list if you’re not sure what to put into the search box.

Unfortunately, the collection is focused on north central USA, but look at the filter a report or article has to go through to make it onto the site:

Criteria for inclusion of a research report or abstract in the compendium includes: 1) at least two site-years of research, with multiple crops or varieties substituting for a site-year; 2) authors listed; 3) replicated with statistical analysis; 4) reasonably applicable to north central USA crop production; 5) reference source available; and 6) author permission.

It’s a great start to building a credible database on the topic. Let us know if you find relevant gardening information by posting a comment below.

Recently ScienceDaily.com posted an article about American chestnut trees due to be planted in New York City. Researchers hope that these trees will be resistant to chestnut blight, an introduced fungal disease that pretty much wiped out mature specimens over the last 100 years.

When I lived in Buffalo, I was a member of the American Chestnut Foundation and every spring I helped with efforts to replant chestnuts in the hopes that resistant individuals might be found. The problem is that the disease doesn’t kill young trees: it can take many years to find out whether a particular tree is resistant or not.

Chestnut suckers from live roots of blight-killed tree. I saw these a lot in western NY forests in the 1990’s.

Part of the earlier research efforts involved crossing resistant European chestnut with American chestnut in hopes of creating resistant hybrids. The downside, of course, is that such offspring would not be “pure” American chestnuts. More importantly to many people, these hybrids might not produce the same quality of nuts.

The research mentioned in the Science Daily article involves creating transgenic plants: a wheat gene resistant to the fungus was inserted into the chestnut genome with the hopes that the resulting trees would be immune to blight. These trees are genetically modified organisms, or GMOs.

It’s worth noting that it’s this kind of work that has been branded as “Frankentree” research, which incites a lot of fear and hysteria. It’s what caused ecoterrorists to mistakenly firebomb the UW Center for Urban Horticulture in 2001 when I was faculty there. It’s what causes people to freak out about eating GMO foods.

So my question for you – does the fact that transgenic chestnut trees will be “on the loose” fill you with fear? Or does it make you hopeful that we’ve possibly found a way to overcome an introduced disease? (As I just noticed in reading this over before posting that I used some form of the word “hope” in nearly every paragraph. I guess it shows where I stand.)

First, let me give a blanket apology for all of us GPs – this is the first time ever all four of us have NOT posted in the same week. I’m on the road this week with my high schooler checking out colleges, and I think the other three are out drinking beer and tipping cows somewhere. So our visiting GP veggie specialist extraordinaire has graciously stepped in to answer a reader’s question about the apparent decline in vegetable nutrition. Here’s Charlie:

Your United States Department of Agriculture tracks information about all kinds of things, like dry bean production and farm wage data. They also measure nutrient content of foods (not pesticide residues–that’s for the FDA). Some curious researchers have wondered if the nutritional content of vegetables has changed since the mid-20th century. The data exist, so why not look through them?

Authors of a well-cited publication from 2004 have done just that. Specifically, Davis, Epp, and Riordan did (J. Amer. College Nutr., 23:669-682). What they found, for example, is if you ate cauliflower in 1950, you probably ate more protein, phosphorous, iron, and thiamin than if you ate the same amount cauliflower in 1999. They measured the ratio of the nutritional concentration in 1999 compared to the concentration in 1950 [smartly, they adjusted 1950 moisture content to match that of 1999]. If ratio was 1, there was no difference in the concentration. If the ratio was 0.5, then 1999 cauliflower had half the nutrition of 1950 cauliflower. They had to use some statistical trickery (they didn’t know error or the number of samples from 1950), but some people might just call that ‘educated assumptions’. When these ‘educated assumptions’ must be made, I’m a big fan of being conservative with them–in this case, that means that if there is a tiny difference, the researchers wouldn’t catch it. Being conservative with statistics makes the differences that show up more robust. Even with the most conservative assessment, the authors show that 26% of the time when nutrients are studied in vegetables, the concentration was lower in 1999 than in 1950. However, 11% of the time, the concentration was higher in 1999.

The primary author of that paper published a summary of evidence in 1999 (HortScience 44:15-19). The average numbers for a bunch of studies show similar declines, but statistically, there seems to be a significant decline in specific nutrients in about &frac14; to ⅓ of vegetables studied over time.

‘Jade Cross’ brussel sprouts

Why would this be happening? Well one reason might be dilution. The review article gave an example of raspberries: growing raspberries with more phosphorous fertilizer gave more yield (on a dry weight basis), and higher phosphorous concentration in the fruit. But the plants still took up the same amount of calcium (or only slightly more), irrespective of how many pounds of raspberries were produced. More pounds of raspberries with the same pounds of calcium removed from the soil means less calcium per pound of raspberries. That makes sense. The plants can make much of their own dry matter (photosynthesis!), but they can’t make calcium. I have some questions about using the dilution argument for the 2004 paper: if dry matter didn’t change, but concentration of macronutrients went down, the concentration of something else had to go up–but what? Is the decline in specific things large relative to the concentration of that thing but small relative to the total dry matter?

‘Graffitti’ cauliflower

The dilution effect may be the cause sometimes, but what causes the dilution effect? Atmospheric CO2, or changes in production practices like irrigation, pest control, and fertility might be important, but I like the ‘breeding’ explanation. Breeders don’t care how much calcium the plant has. They care if it yields well (dry matter), is resistant to pests and diseases, is pretty or unusual, tastes good, etc. If a trait is not selected for in a breeding program, it might go away over time. So maybe the answer is to breed veggies that accumulate (or make, if it’s a vitamin) more nutrients, or to grow more of the existing varieties that might, by chance, already have relatively high nutrient concentrations (they do exist). There may be a market for selling broccoli that has certifiably more calcium in it, and for change to happen in the marketplace, it has to be profitable. For right now, you have no idea if the broccoli you buy is a low-calcium or a high-calcium variety because consumers don’t demand to know.

The un-interesting headline reads “some vegetables may be declining in average nutrient concentrations over time”. The interesting (and false)
620
headline would be “vegetables aren’t good for you anymore”. From the cauliflower example above: in 1999, a serving of cauliflower would have about 2.5% of your recommended daily iron, 6.3% of your phosphorous, 3.5% of your protein, and 4.8% of your thiamine. In 1950, it would have been 6.1% of your iron, 10.3% of your phosphorous, 4.3% of your protein, and 9.2% of your thiamine. Your vegetables aren’t devoid of nutrition, they’re good for you. Easter candy probably has none of those things. If you’re worried, have a multivitamin, or better yet, eat MORE vegetables. But vegetables grown in 1950 are rather old by now, I’d avoid them if I were you. Meanwhile, know that a) science is aware of the issue, b) it’s not universal.

One of the underlying tenets of ecology is the principle of competitive exclusion. This principle states that when two species compete for the same vital resource, the better adapted species will ultimately displace its competitor. Simply put, it’s survival of the fittest.

More recently, some ecologists have suggested that nature’s not quite so brutal – that the species composition in an ecosystem is determined more by random fluctuations in population numbers than by direct competition.

But last month, this "neutral theory" was directly challenged by evidence on three continents which compared the abundance of particular tree species, both in the fossil record and in existing forest ecosystems. The similarities were so close among all the comparisons that it’s most likely due to direct competition rather than random fluctuations.

While this information might seem pretty esoteric, it does have direct application to gardens and landscapes. Among your plants, you will have some that compete better for water, nutrients, and other resources. The concept of "companion plantings" as plants actively helping each other survive is a wishful projection on our part.

And this all ties into the discussions we’ve been having about mulch. While living mulches – turf, ground covers, etc. – help protect soil structure and reduce erosion, they also compete with other plants in the landscape. Maintaining landscapes with living mulches will require more water than the same landscape with organic mulches. It doesn’t matter if the plants are native or not – it’s just a question of limiting resources and who’s going to be the most competitive in extracting them.

(Forgot to include the reference the first time I posted this – here it is: Ludwig-Maximilians-Universitaet Muenchen (LMU). “Jostling for position: Competition at the root of diversity in rainforests.” ScienceDaily, 26 Jan. 2012.)